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Corporate IESO > Media > About Public Appeals > IESO Declares Power Warning as Hot Weather Strains System

IESO Declares Power Warning as Hot Weather Strains System

August 2, 2005

Ontario's Independent Electricity System Operator (IESO) has elevated its appeal for reduced electricity use to a Power Warning and is now asking consumers to immediately reduce their use of electricity in order to alleviate the increased strain on Ontario's electricity system.

"The supply outlook for the rest of today has deteriorated resulting in the need for a Power Warning, a stronger appeal than was issued yesterday morning," said Paul Murphy, Chief Operating Officer for the IESO. "The IESO has implemented a voltage reduction in order to reduce demand and manage the reliability of the power system," added Murphy.

This Power Warning is in effect until 8:00 p.m. EDT.

Power Warnings are issued by the IESO during periods of high demand for electricity, when supplies of reserve power are low. Any further reduction in transmission or generation availability or any increase in demand could create shortfalls of electricity. If all sources of supply are exhausted, the IESO will take protective actions such as a system voltage reduction, or rotating power cuts, if necessary. In these circumstances, no additional public notice may be possible.

Consumers and businesses can reduce the demands on the electricity system by immediately:

- Turning off all but essential internal and external lights;
- Setting air conditioners to 26 degrees Celsius or higher, or using fans as an alternative;
- Closing curtains and blinds to keep out the sun and retain cooler air inside; and 
- Delaying the use of major power-consuming equipment such as dishwashers, washers and dryers and swimming pool pumps until after 8:00 p.m.

The IESO is responsible for managing Ontario's bulk electricity system and operating the wholesale electricity market. For more information, visit